430 



PITS AND FRAMES 



of these changes being to enable the cul- 

 tivator to add to or renew the bed with- 

 out disturbing the plants in the frame, 

 which could be lifted off or elevated for 

 the time. Some have suggested similar 

 movable frames, making them to slide 

 from the exhausted bed to another pre- 

 pared for it made up at one of the ends. 



Were such an arrangement worth con- 

 sideration, we would suggest placing a 

 cast-iron rail, supported on pillars, along 

 the back and front of the intended beds, 

 and mounting the frames on iron rollers 

 or wheels, by which means they could be 

 moved backwards and forwards with 

 much greater facility. 



It is difficult in all dung-beds to main- 

 tain a proper atmospheric heat. To re- 

 medy this, Mr Knight proposed admit- 

 ting air slightly warmed to improve the 

 internal heat, as well as to produce ven- 

 tilation by admitting air from below 

 instead of by opening the sashes, which at 

 all times is a most inadequate, and often 

 dangerous, mode of ventilating frames or 

 pits — as the pure air admitted at front 

 passes over the foliage and escapes at the 

 back, without dislodging the foul and 

 stagnated air just above the surface of 

 the mould; while, in addition, that air is 

 seldom sufficiently warm to be so admit- 

 ted with safety to the plants. The fol- 

 lowing diagram, fig. 594, will explain its 



Fig. 594. 



principles. A metallic tube, the orifice of 

 which is at a, is laid about 1 foot under 

 the top of the bed : from this the three 

 short upright tubes b b b proceed, and 

 open into the atmosphere of the frame. 

 The end of the long tube at c is furnished 

 with a stopper, by which the draught 

 of the other tubes is regulated. These 

 tubes should be, we think, perforated so 

 as to admit the heat and gaseous mois- 

 ture from the dung more readily, and the 

 orifice should be in shape of a wide fun- 

 nel, for more readily admitting the cold 



air to become heated. We had also, with- 

 out previous knowledge of Mr Knight's 

 experiment, practised a somewhat similar 

 plan even at a prior date. 



The other principal improvements on 

 pits and dung-frames, but of which it is 

 deemed unnecessary to give illustrations, 

 are the meridian pits of Neeve, of which 

 excellent figures are given in " The Ency- 

 clopaedia of Gardening," " The Gardeners' 

 Magazine," &c, — the chief merit of which 

 consists in elegance of appearance — and 

 the revolving frame, invented and partially 

 described by Mr Gawen of Shirley, near 

 Southampton, and Mr Alexander Bisset, 

 late of Methven Castle, near Perth, much 

 about the same time, and almost on the 

 same principle, and certainly without 

 any communication existing between the 

 parties. These inventions, however, have 

 not been followed up; and, so far as we 

 are aware, were exemplified only by the 

 inventors themselves. 



Were revolving frames worth consider- 

 ation, as we think they are not, far more 

 simple and effective means to produce the 

 movement than the one referred to above 

 may be seen at every railway station — 

 viz., the revolving tables upon which the 

 carriages are placed when a change in 

 their position is desired. 



The German hotbed is often half sunk 

 under the surface of the ground, and is 

 in very common use in Germany and the 

 north of Europe. It is composed of 

 stable manure, leaves, and tan, mixed or 

 separate according to circumstances. On 

 the Continent it is a very common prac- 

 tice to sink the dung-beds under the sur- 

 face. The intensity of cold to which they 

 are exposed during winter led, no doubt, 

 to this practice ; but we do not think the 

 system is a wise one, because the conduc- 

 tion of heat into the earthy banks that 

 surround the mass is more than would 

 be lost by building them on the surface, 

 and thatching them with faggots and 

 coverings of straw, reeds, or any other 

 non-conducting material. 



Probably this fact led to the erection 

 of pits walled all round, and afterwards 

 to the walling in of the linings, as exem- 

 plified in most pits built on the best 

 principles. No doubt having the heating 

 materials under the surface prevents the 

 cold winds from driving the heat from 

 one part of the bed to the other, while 



